This invention relates to electromedical apparatus and particularly to medical electrode catheter apparatus. The device is particularly useful as a transvenous electrode catheter for use as part of an implantable cardiac defibrillation system.
In the past, various catheter or lead electrode devices have been used and proposed for use in conjunction with implantable cardiac defibrillator devices to automatically provide a current pulse to the heart upon the occurrence of a predetermined cardiac event, such as tachycardia for example. However, the prior art devices are generally complex, difficult to construct and utilize, and are inefficient to use. A particular problem present in prior art devices is the phenomenon of uneven current distribution around the electrodes of the catheters or leads.
The first defibrillation catheter with coil-type electrode of which the inventors are aware is disclosed in U.S. Pat. No. 3,614,955 (Mirowski) and U.S. Pat. No. 3,942,536 (Mirowski). U.S. Pat. No. 4,355,646 (Kallok) shows solid rings for electrode "coils". U.S. Pat. No. 4,499,907 (Kallok) depicts a defibrillator catheter with an integral resistor to limit current to the entire electrode coil. It does not, however, affect the current distribution at the ends vs. the center of the electrode. U.S. Pat. No. 4,603,705 (Speicher et al.) discloses a defibrillator catheter combining pacing functions. U.S. Pat. Nos. 4,860,769 and 4,865,037 (Fogarty) show a coiled ribbon and a coiled catheter tip. U.S. Pat. No. 4,932,407 (Williams) discloses a ribbon coil. These prior art defibrillation catheters have lead connections at one or both ends of their respective electrodes. U.S. Pat. No. 4,969,463 (Dahl) shows a catheter which allows control of the energy delivered to different parts of the coil. The coil is broken up into several rings and each has its own conductor. Thus, each section can receive a different pulse. However, such a design would be impractical to use with the multiple conductors required.
Despite the need for a cardiac defibrillation catheter in the art which provides optimized field distribution, and which overcomes the limitations and problems of the prior art, none insofar as is known has been proposed or developed. Accordingly, it is an object of the present invention to provide a cardiac defibrillation catheter which yields optimized field distribution, and which is easy to construct and utilize.